MAG61 with compact NTC soft starter (lots of pictures)

[void87]

Hello everyone.
The flashlight fever got me recently, and i decided to build my first hotwire, a Mag 5761 with parts from Kai including the 2 D-cell LiIon pack. Because of the length of the pack i couldn't use the stock or even the shortened spring for making contact, and adding an NTC to the whole thing was a pain... However i found an easy way to put an compact softstarter into the tailcap instead of the fat spring:

Here's the light:





And the tailcap with softstarter:





Its very simple to build, you just need a circuit board,a spring, some wire and the NTCs

And the best thing it works with cells fresh off the charger with 8,36V without instaflashing:


Compared to my Ultrafire WF-500 (right), picture made with daylight, it wasn't dark:


So it's possible to make a good light with cheapo Parts from KD
Parts used:
-Mag 2D
-KAI SMO Reflector V2
-KAI G4 bulb holder
-KAI Coated 52mm lens
-KAI2 D-cell LiIon pack
-Some wire
-Circuit board
-A spring
-3x 1R NTC in parallel (http://www.epcos.com/inf/50/db/ntc_06/ICL__B57237__S237.pdf)



**I added some content afterwards, hopefully this thread is somewhat more interesting now

Hope this helps somehow

 

[Aircraft800]

Re: Simple, compact NTC soft starter

Wow!
That is a nice clean build! Congratulations!

Now you sickness has begun, enjoy the ride!

How does your lite do off a fresh charge of 8.4v? Usually this is enough to the bulb even with the resistance of the switch, spring, etc..

 

[void87]

My charger stops at 8,36V, i can use the light at once.

 

[Chodes]

Looks good.

Regarding the D LIONs not fitting - was it the Golden Shorty Mag spring from Kai you tried? (Kai states these springs will allow 2 x D LION to fit in a mag 2D) Just curious as this is a combination I was considering.

Also , how is the NTC board retained in the cap? Or does is just sitting there, held securely once light is assembled?

 

[2xTrinity]

Re: Simple, compact NTC soft starter

Wow!
That is a nice clean build! Congratulations!

Now you sickness has begun, enjoy the ride!

How does your lite do off a fresh charge of 8.4v? Usually this is enough to the bulb even with the resistance of the switch, spring, etc..

The 5761 flashes at 7.9V, nearly 6 amp draw. That means that 100mOhm resistance is enough to protect the bulb (a drop of about 0.6V, or 7.8V from an absolutely fresh LiIon cell). The combination of the Kai cells internal resistance, resistance from the protection board, resistance in the switch etc. should be about 200mOhm, so no the 5761 won't instaflash.

Regarding the D LIONs not fitting - was it the Golden Shorty Mag spring from Kai you tried? (Kai states these springs will allow 2 x D LION to fit in a mag 2D) Just curious as this is a combination I was considering.

Yes, this will work for the mag 2D, though if you get indepndent cells and not the two cell pack it will be tighter. Another way to make space (eg, if you want to fit 3 in a 3D, or 4 in a 4D) is to thin out the mag switch as much as possible using a dremel -- it's possible to remove a fair amonut of useless plastic from the bottom. The switch can also be installed higher up so that the switch is no longer perfectly centered in the opening, but closer to the top, as well. I had to do all of these to fit 4 Kai D-Cells in a 4D Mag.



I actually had a 2d Mag 61 (individual kai cells, not the 2D pack) for some time, though I recently cannibalized it to make the 4D hotwire I was describing. With a soft starter, the cells are able to deliver fairly high currents, without it though they won't light up anything brighter than a ROP low due to the fact that the short circuit protection responds too quickly.

For example, right now I have 4 Kaidomain D-Cells inside a 4D mag, with the AW 3-level switch happily lighting up an Osram 64623 at nearly 10 amps, as white and bright as many of my other hotwires, or Osram 64611 for half the brightness, double the runtime on high. (Osram 64625 and 64610 both instaflash off four Kai cells)

I believe I have the only >100W mag capable of running >20 minute (not continuously...) on high, along with a "low" output mode that's still nearly as bright as an ROP hi :devil: In the near future I plan to introduce a couple failsafes however -- a magnetic reed switch as an emergency "kill switch" (light only works if the magnet is attached), and a temp probe in the head that will kill the light if it surpasses a temperature I feel is too high.

Both measures are to prevent a repeat of what recently happened where guest turned on my 2D Mag61 then inadvertently set it bezel-down on a table, still on... luckily it was on low and I caught it within a couple minutes...

 

[Chodes]

Thanks for the info.
I have a D size AW driver so it sounds like 2D LIONs ,5761,and a 2D will make a good combo. I won't be pushing the cells nearly as hard as you have been.
Good to know the 2 Cell pack is that little bit shorter.

 

[LuxLuthor]

Nice job void87, and welcome to CPF !

 

[void87]

Looks good.

Regarding the D LIONs not fitting - was it the Golden Shorty Mag spring from Kai you tried? (Kai states these springs will allow 2 x D LION to fit in a mag 2D) Just curious as this is a combination I was considering.

Also , how is the NTC board retained in the cap? Or does is just sitting there, held securely once light is assembled?

I tried the method "Northern Lights" used in his mag: http://www.candlepowerforums.com/vb/showthread.php?t=177344 (scroll down, there's a picture of it) and found it to tight. The KAI golden shorty spring will be ok without the mentioned construction but with an extra insulator and contact on top it was scratching and denting the battery bottom.


Just a question for those with a SMO Reflector and 5761: does it focus properly?? The stock mag had a laser like beam, but now it isn't that nice anymore